I am having this same problem, I can't get any audio from my DVD when it is playing through any program, yet all my other sounds work including streaming video... HELP! I am on an XPS M1210 and trying to use Cineplayer... or Windows Media Player - neight have audio... HELP!
Call up dell and tell them that you need to reinstall the DVD Decoder software. They'll ship you the software. That was my problem. They hadn't included the software when I bought the laptop. When I needed to re-install it, I didn't have it. Mine was called WIN-DVD if I recall correctly.
Just to let you all know, today I found the solution. It was an easy one, too! Dell has a software patch for Sonic CinePlayer 3.0, that solves this problem. File Name R142470.EXE. My problem was solved in 3 minutes!